Viewport pivot point changed from scene objects to around viewport camera origin
It sounds like you centered the view on the camera.
Here are some ways to set the view center:


ShiftB or 3D view header > View > Zoom Border (Note that this will also zoom to fit the view to the defined border)
Select an object/vert/face/spline etc. and press Numpad . (period) to center the view to the selection.
Press ShiftC to center the view to the world origin (default). Note this will also center the 3D cursor.


If none of these work, then it sounds like you have Locked the view pivot to the camera object (ShiftNumpad .). See if there is any object  selected in the Lock to object option in 3D view > Properties region (N) > View > Lock to object:



You can remove this lock by clicking the X next to the object name, or pressing AltNumpad ..



CtrlShiftAltC is a shortcut for snapping object origins. (it does not affect the view)